In the treatment of water for drinking purposes or of waste water prior to discharge, it is conventional practice to disinfect the water for elimination of potentially harmful microorganisms. It has long been conventional practice to utilize chlorine in liquid or gaseous form as the biocide to accomplish this task. Recent investigations have pointed out the potential disadvantages of chlorination due to formation of harmful by-products. Interest has increased, therefore, in the use of other biocides such as ultraviolet radiation and ozone.
It is well known that ultraviolet radiation at a wave length of 2537 A is an efficient germicide. This is described by Czulak et al. in U.S. Pat. No. 3,336,099, issued Aug. 15, 1967. It is also known that the output of a lamp designated to produce 2537 A wave length is optimum at a particular operating temperature. Temperatures either warmer or cooler than the optimum will produce lower output of radiation. Further, it is also known that when air is subjected to ultraviolet radiation, at a wave length of 1875 A, that ozone is produced from oxygen contained in the air.
As is disclosed in U.S. Pat. No. 3,336,099, waste water and air can be treated simultaneously by ultraviolet radiation in apparatus having a single lamp, and the treated water can then be contacted in a storage tank by the ozone that is produced to further purify the water. However, the construction and arrangement of the apparatus disclosed in this patent fails to provide the efficiency of ultraviolet radiation to eliminate harmful microorganisms while simultaneously optimizing the ozone production potential from the ultraviolet radiation source. In the disclosure of this patent is is contemplated that the air to be irradiated should be cooled after passing through an air compressor, but when the cooled air is then passed in contact with the lamp it must flow at a sufficiently rapid rate so that if the temperature of the lamp is maintained in a range wherein desired radiation efficiency is achieved, the ozone concentration of the air is relatively low. Thus, high radiation efficiency and optimum ozone concentration cannot be achieved simultaneously.